Add Data View Mapping

[Daniel Marsh-Patrick]

Map data roles (defined in #3) to the data view. Matrix should be sufficient for this. Map category to columns and sampling to rows.

Add the following conditions:

• Category: max 1
• Sampling: max 1
• Measure: max 1

We may relax this in future, if we need to enable drilling.

[Daniel Marsh-Patrick]

#4: Added matrix data view mapping. Resolves #4.

→ <<cset 1f666c5e5462>>